It is well known by boat owners and operators that boat hulls require frequent maintainence, especially if the boat is docked in a salt water harbor. Regardless of the material which forms the hull, and regardless of the type of paint or other finish on the surface of the hull, barnacles, mineral deposits, algae, and other detritus of the sea quickly attach to the hull, altering the laminar flow lines of the hull and slowing the ship. The unfortunate result, for commercial boats, is the necessity to consume more fuel. For pleasure craft, the buildup of deposits on the hull is noticed more in the deterioration in the performance of the boat.
Consequently, it is necesssary regularly to remove a boat from the water and refinish the hull. Such refinishing usually requires scraping and removing the larger deposits, sanding the hull until smooth and streamlined once more, and then repainting the hull with paint that resists the corrosive effects of the sea. The devices available in the prior art for sanding the hull include disc sanders, vibrating orbital sanders, and belt sanders. Disc sanders are well known to cause gouges and irregular surface finishes, and are therefor unsuitable. Orbital sanders are extremely slow at removing surface material, and are thus suitable for the final steps of finish sanding, after the surface has been smoothed substantially. The only device that remains for performing most of the sanding work on a hull is the belt sander.
The standard belt sander known in the prior art employs and endless sanding belt circulating about a pair of pulleys, with an electric or gasoline motor driving one of the pulleys. The pulleys are generally no more than 12 inches apart, so that the effective sanding area is rather small. Also, a pressure plate is generally provided to support the portion of the belt which contacts the workpiece. The pressure plate is generally rigid and inflexible, so that the typical belt sander is suited for forming smooth planar surfaces.
However, the suitability of the typical belt sander for forming smooth, planar surfaces is a detriment for working on a curved boat hull which generally has no planar surfaces whatsoever. Due to this fact, extreme care must be taken in using a belt sander on a boat hull. The flat, rigid pressure plate of the sander tends to impinge the sanding belt onto the hull in an uneven fashion, causing streaking and gouging of the surface. For a skilled operator extreme care must be exercised at all times so that the hull may retain its smooth and streamlined configuration.